Rotas de beneficiamento para recuperação de minerais portadores de ferro do underflow do espessador de lamas da usina de Brucutu

Abstract

Routes were investigated for the concentration of iron minerals contained in the slimes thicken er of the Brucutu plant aimed at producing pellet feed for direct reduction and minimization of tailingsgeneration. The current rateof underflow in the slimes thickener at the Brucutu plant is approximately 270t/h and can reach up to 370t/h, due to the future expansion of the processing plant. Chemical analysis showed the following contents: Fe 46.0%, 15.0% SiO2, 10.0% Al2O3, PPC 10.0%, P 0.16%, Mn 0.15%. Samples of small and large volume (the same sample used in the concentration tests) were submitted to chemical and mineralogical characterizations as well as pH and percentage of solids determinations, and size analysisby cyclosizer. The results of this stage showed high levels of botrioidal goethite in the +10µm fractions, followed by lamellar hematite as the second iron carriermineral. The -10µm fraction has a large quantity of clay minerals, mainly kaolinite, with earthy goethite associated. Three concentration routes were proposed. The first route (route A) was based on pilot testing of magnetic concentration as a rougher stage and flotation in conventional cell as cleaner stage. The second route (route B) was used only in bench scale flotation tests (rougher and cleaner). The third route (route C) was carried out with the gravity concentrator Falcon. The tested stages were rougher, followed by three scavenger stages. A fourth route of magnetic concentration (route D)was also tested in exploratory experiments. The defined stages were rougher, cleaner, scavenger I and scavenger II (or cleaner of the scavenger). A sample was taken exclusively for this test and it was not submitted to mineralogical characterization, as the others. From the all analysis it was concluded that the best overall result was achieved from the "route D". Whereas the deployed project, from of this scenario, could be recovered around 12.7% of all mass produced in the underflow of the slimes thickener of the Brucutu. The calculated total production would be around 363,026t/a, Fe 66.8%,SiO20.8%, P 0.05%, Al2O30.97%and PPC 2.45%. It is expected,therefore,that after the project implementation, the generated product is inserted into the VALE product portfolio. The total mass of waste should be decreased, the life of the tailings dam increased, and resulting environmental impacts will be mitigated or even avoided.